Plastic nozzle plates that have ink chambers and conduits built-in need a means of attachment to the underlying semiconductor chip. In current designs, the chambers and other ink flow features are created by essentially conventional photo etching using a thick film photoresist layer applied to a semiconductor chip. Photoresist remaining after the imaging and etching operation is left in place and used as an adhesive layer.
The remaining photoresist is an effective adhesive because current techniques only partially cure the thick film photoresist. The lack of complete cross linking of the resist layer imparts an adhesive property to it which is used for bonding the nozzle plate down by applying temperature and pressure.
To reduce costs and to eliminate a major source of misalignment between the ink heaters or chambers and nozzle holes, it is desirable to use a single-structure nozzle plate with integrated flow features and nozzle holes built in. Several techniques may be utilized to achieve the integrated nozzle plate, such as laser machining and injection molding. In each case it is generally possible to apply an adhesive layer for connection of the nozzle plate to the underlying semiconductor chip. Heat and pressure can be applied to activate such adhesive since the nozzle plates, although they are polymer films, may be made of selected polymer materials which do not melt or degrade at the temperatures required.
Such an added layer is costly in terms of material and operation steps. Moreover, certain molded plastics, typically those of homogeneous polymeric material, cannot be used at such temperatures because the nozzle plate would melt or deform. Moreover, it is also difficult, if not impractical, to apply the adhesive layer to individual film nozzle plates after their manufacture.
Accordingly, it is the primary feature of this invention that a separate adhesive layer is avoided in the bonding of a film nozzle plate to a semiconductor chip having drop-ejection heaters for nozzles of the nozzle plate.
This invention employs adhesion by melt contact. It is widely known that such adhesion is a function of roughness or irregularity of the surfaces involved, and a preliminary roughening step may be employed in accordance with this invention.